JP3095508B2 - Demodulator for spread spectrum communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demodulator for spread spectrum communication having a cyclic integrator for averaging a correlation output.

[0002]

2. Description of the Related Art A conventional demodulator for spread spectrum communication will be described below with reference to the drawings.

FIG. 3 is a block diagram showing the configuration of a conventional demodulator for spread spectrum communication. In FIG. 3, an input terminal 1 to which an incoming pseudo-noise signal is input and a multiplier 3 to which a pseudo-signal generating unit 2 is connected are connected to an integrating circuit 4, and an incoming pseudo-noise signal from the input terminal 1 and a pseudo signal The signal is multiplied by the pseudo-noise signal on the receiving side from the generator 2 and output to the integrating circuit 4. The multiplier 3 and the integrating circuit 4 form a sliding correlator 5.
Performs the product-sum operation of the incoming pseudo-noise signal and the receiving-side pseudo-noise signal for one information data period at a certain phase difference, and performs the same operation sequentially for all the phase differences of the receiving-side pseudo-noise signal. Perform synchronization acquisition. The adder 6 to which the output terminal of the integration circuit 4 is connected is connected to the shift register 7, and the output terminal of the shift register 7 is connected to the adder 6. The adder 6 and the shift register 7 constitute a cyclic integrator 8, and further integrate the output from the correlation unit to average the correlation. An acquisition control unit 9 to which the output terminal of the shift register 7 is connected controls synchronous acquisition based on the output from the cyclic integrator 8. Further, the synchronization tracking unit 10 to which the acquisition control unit 9 and the input terminal 1 are connected is connected to the pseudo signal generation unit 2, and uses the output from the acquisition control unit 9 to receive the pseudo-noise from the pseudo noise signal generation unit 2. The synchronization tracking is performed so that the incoming pseudo-noise signal and the reception-side pseudo-noise signal are synchronized while controlling the phase of the signal. Further, the data demodulation unit 11 to which the output terminal of the integration circuit 4 is connected is connected to the output terminal 12, and the data demodulation unit 11 demodulates the data and outputs reproduced data from the output terminal 12. Here, the pseudo noise signal on the receiving side is
R> In-phase or out-of-phase signal similar to the sound signal.

The operation of the conventional demodulator for spread spectrum communication configured as described above will be described below. First, an input signal SI i, j which is an incoming pseudo noise signal
Is input to the sliding correlator 5 and multiplied by the multiplier 3 with the pseudo noise signal SL i, j having a certain phase difference from the input signal SI i, j of the output from the pseudo noise signal generator 2 and then integrated. The signal is integrated by the circuit 4. Then, the pseudo-noise signal generating unit 2 sequentially changes the phase difference to change the pseudo-noise signal SL i,
j , and the sliding correlator 5 performs the same operation for all N phase differences. And
This series of operations is further repeated, and when the output is cyclically integrated M times by the cyclic integrator 8, the output Jk
Is, for each phase difference k (1-N),

(Equation 1) k: phase difference between the input signal and the pseudo noise signal N: number of spreading chips M: number of cyclic integration Based on these outputs, an acquisition completion signal is sent from the acquisition control unit 9 to the synchronization tracking unit 10, and the synchronization tracking unit 10 controls the incoming pseudo noise signal from the pseudo noise signal generation unit 2 while controlling the phase of the incoming pseudo noise signal. At the same time, the synchronization tracking is performed so that the noise signal and the pseudo-noise signal on the receiving side are synchronized. At the same time, the data demodulator 11 determines the polarity of the output of the sliding correlator 5 to demodulate the data, and outputs the reproduced data from the output terminal 12. I do.

At this time, the time t required for the capture control unit 9 to transmit the capture completion signal is t> M × N2 × T T: information data period, and the time t is not smaller than M × N2 × T. Absent.

[0006]

However, in the conventional demodulator for spread spectrum communication, for example,
Even in a high-quality transmission line in which it is not necessary to perform cyclic integration twice, as in the case of a transmission line that does not require cyclic integration, a time of M × N2 × T or more is required uniformly until the completion of synchronization acquisition.

The present invention solves the above-mentioned conventional problem. In a high-quality transmission line in which it is not necessary to perform M-time cyclic integration, synchronization can be performed without increasing the probability of false synchronization and without increasing the size of the device. It is an object of the present invention to provide a demodulator for spread spectrum communication capable of shortening an acquisition time.

[0008]

In order to solve the above problems, a spread spectrum communication demodulator according to the present invention outputs a pseudo-noise signal on the receiving side having the same phase or opposite phase as an incoming pseudo-noise signal. A pseudo-noise signal generating section capable of changing the phase of the pseudo-noise signal on the receiving side, and a correlating section for performing a product-sum operation on the incoming pseudo-noise signal and the pseudo-noise signal on the receiving side for one information data period to acquire synchronization A cyclic integrator that further integrates the output from the correlation unit to average the correlation, and uses the output from the cyclic integrator to calculate the phase of the reception-side pseudo-noise signal from the pseudo-noise signal generation unit. A synchronization control unit that performs synchronization tracking so that the incoming pseudo-noise signal and the reception-side pseudo-noise signal are synchronized while controlling, and calculates an output variance from the correlation unit, and then performs a cyclic integration from the cyclic integrator Where the output variance is The minimum cyclic integration count of the cyclic integrator to be in the range is obtained by a cyclic integral control unit for adaptively setting control.

[0009]

With the above arrangement, the cyclic integration control section reads the variance of the sliding correlation output, calculates the variance of the sliding correlation output for all phase differences, and sets the variance of the cyclic integration output thereafter within the predetermined range. Adaptively minimize the number of cyclic integration of
For example, if the variance of the cyclic integration output is set within a predetermined range in a high-quality transmission path that does not need to perform cyclic integration even M times, the probability of false synchronization can be suppressed to a certain value or less, and the number of cyclic integrations can be reduced. And the synchronization acquisition time is shortened.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. It is to be noted that components having the same functions and effects as those of the conventional example are denoted by the same reference numerals and description thereof is omitted.

FIG. 1 is a block diagram showing a configuration of a demodulator for spread spectrum communication according to an embodiment of the present invention. In FIG. 1, a cyclic integration control unit 21 connected to a connection point between the integration circuit 4 of the sliding correlation unit 5 and the adder 6 of the cyclic integrator 8 is connected to the shift register 7 of the cyclic integrator 8 and all positions are controlled. In order to calculate the variance of the sliding correlation output with respect to the phase difference and suppress the false synchronization probability to a certain level or less, the number of cyclic integration of the cyclic integrator 8 is adaptively reduced as much as possible within a predetermined range of the variance of the cyclic integration output. This is a configuration in which the setting is controlled so that

The operation of the demodulator for spread spectrum communication configured as described above will be described below. First, the input signal SI i, j is input to the sliding correlator 5, and the multiplier 2 outputs the pseudo noise signal SL i, j having an output signal from the pseudo noise signal generator 2 and having a certain phase difference from the input signal SI i, j . After being multiplied by j , it is integrated by the integration circuit 4. Then, the pseudo noise signal generation unit 2 outputs the input signal SI
phase difference k (1 to N) between i, j and pseudo noise signal SL i, j
Are sequentially changed, and the same calculation operation is performed for all N phase differences. The output Jk is the phase difference k (1 to
N)

(Equation 2) Becomes Then, the output Jk is read by the cyclic integration control unit 21, and the variance for all the phase differences is calculated.

By the way, if the noise mixed in the input signal is white noise and the variance of the cyclic integration output is kept within a predetermined range in order to suppress the probability of false synchronization, when the variance of the sliding correlation output is determined, the minimum cyclic The number of integrations is uniquely determined.

Therefore, the root mean square of the values calculated above is
Based on (variance), the minimum number of cyclic integrations M ′ in which the variance of the subsequent cyclic integration output falls within a predetermined range is calculated, and the information is sent to the cyclic integrator 8. Then, the output Sk of the sliding correlator 5 is cyclically integrated by the cyclic integrator 8 M ′ times,
Based on the output, the acquisition control unit 9 sends an acquisition completion signal to the synchronous tracking unit 10. In the synchronous tracking unit 10, the pseudo noise signal generating unit 2
At the same time as performing synchronous tracking while controlling the phase of the pseudo-noise signal from the CDMA, the data demodulator 11 determines the polarity of the output of the sliding correlator 5 and demodulates the data.
To output playback data.

When the noise mixed in the input signal is white noise, the variance of the sliding correlation output decreases as the quality of the transmission path increases, and the variance of the cyclic integration output increases as the number of cyclic integration increases. Becomes smaller. That is, since the conventional cyclic integration number M is set so that synchronization can be acquired even when the transmission path is very bad, in the case of a normal transmission path, (minimum cyclic integration number M ') <
(Conventional cyclic integration frequency M). At this time, the time t 'required for the capture control unit 9 to transmit the capture completion signal is t' = M '× N2 × T <t where the time t is the time required for transmitting the conventional capture completion signal. In addition, the synchronization acquisition time can be reduced without increasing the probability of false synchronization.

Although the sliding correlator 5 is used in the present embodiment, as shown in FIG. 2, one period of the incoming pseudo noise signal a and the reception pseudo noise signal b stored in advance are used. A matched filter correlator 31 for simultaneously acquiring and correlating each chip for one cycle to perform synchronous acquisition may be used, and the matched filter correlator 31 may have the same number of stages as the length of the incoming pseudo-noise sequence and the receiving-side pseudo-noise sequence. , A multiplier 33 for multiplying the signals from the respective stages of the shift register 32, and an adder 34 for adding the output from the multiplier 33. The adder 34 outputs a correlation output c. . This is a method of performing initial acquisition by performing pattern matching between an incoming pseudo-noise sequence and an internally stored receiving-side pseudo-noise sequence.

[0017]

As described above, according to the present invention, the output variance from the correlation section is calculated, and the minimum number of cyclic integrations of the cyclic integrator is adapted so that the variance of the subsequent cyclic integration output falls within a predetermined range. By providing the cyclic integration control unit for performing the setting control, the synchronization acquisition time can be reduced without increasing the probability of false synchronization and without making the apparatus too large.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a demodulator for spread spectrum communication according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a matched filter correlation unit of a demodulator for spread spectrum communication according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional demodulator for spread spectrum communication.

[Explanation of symbols]

 2 Pseudo-noise signal generator 3, 33 Multiplier 4 Integrator 5 Sliding correlator 6, 34 Adder 7, 32 Shift register 8 Cyclic integrator 9 Capture controller 10 Synchronous tracking unit 21 Cyclic integration controller 31 Matched filter correlator

Claims (1)

(57) [Claims] 1. A pseudo-noise signal generator for outputting a pseudo-noise signal on the receiving side having the same phase or opposite phase as an incoming pseudo-noise signal and capable of changing the phase of the pseudo-noise signal on the receiving side. A correlation unit that performs a product-sum operation of the incoming pseudo-noise signal and the reception-side pseudo-noise signal to acquire synchronization, and a cyclic integrator that further integrates an output from the correlation unit to average the correlation. And synchronizing tracking so that the incoming pseudo noise signal and the reception pseudo noise signal are synchronized while controlling the phase of the reception pseudo noise signal from the pseudo noise signal generation unit using the output from the cyclic integrator. Calculating the output variance from the correlation unit, and adapting the minimum number of cyclic integrations of the cyclic integrator so that the variance of the cyclic integration output from the cyclic integrator thereafter falls within a predetermined range. Cyclic integral control with dynamic setting control Spread spectrum communication demodulation device that includes a part.